Underfeed furnace



May 8, 1923. 1,454,697 M. .1. WIGHTMAN UNDERFEED FURNACE Filed May 261919 2 Sheets-Sheet l BY 55m/ ATTORNEY May 8, 1923.

M. J. WIGHTMAN UNDERFEED FURNACE 2 Sheets-'Sheet 2 Filed May 26 1919INVENTOR Melle L Moy/Ilia ATTORNEY MERLE J. WIGHTMAN, 0F SEATTLE,WASHINGTON.

UN'DERFEED FURNACE.

Application filed May 26, 1919. Serial No. 299,805.

To all w/Lom it may concern Be it known that I, MERLE J. VIGHTMAN, acitizen of the United States, and resident of Seattle, in the county ofKing and State of lVashingtomhave invented certain new and usefulImprovements in Underfeedv Furnaces, of which the following is an exactand clear specification.

My invention relates to improvements in underfeed furnaces and toimprovements in automatically operated mechanical devices for supplyingcoal and air to such furnaces and the object of my improvement is toprovide a furnace which iscapable of consuming coal eiiciently and ofsecuring practically perfect combustion of the coal regardless of therate at which the coal is fed to the furnace.

Another object is to provide means for regulating the rate at which thecoal is fed to the furnace and automatic means for regulating the supplyof air in the correct proportion to the supply of coal, it having beenfound that the relative proportions of coal and air vary for differentrates of feeding.

A further object is to provide openings at a plurality of differentpoints in the firepot between the top and bottom thereof through whichair for the purpose of combastion may be admitted such fire pot hav-vlng devices therein for rotating the coal and being provided with astationaryi spiral thread for working live coals from the top of the potdownwardly into the bodyof the coal t0 ignite the main body of the coaland commence the gasification and distillation of such coal so that itwill be in a proper state for combustion when it reaches the point atwhich the actual combustion takes lace.

Still further objects are to provide a furnace that is particularly welladapted to be constructed in small sizes for domestic use and one thatis provided with an electric ignition system for lighting the re in thefire pot.

The invention consists in the novel construction, adaptation andcombination of interdependent parts of a mechanically stoked, underfeedfurnace as will be more clearly hereinafter described and claimed.

In the accompanying drawings Figure 1 is a view in vertical mid sectionof a furnace constructed in accordance with my invention, certain partsbeing shown in elevation and other parts being omitted. Fig. 2 is a viewin cross section on broken line 2-2 of Fig.4 1certain parts being shownin plan; and Fig. 3 is a view in side elevation of the mechanicallylactuated coal and airfeed mechanism.

Like reference numerals designate like parts throughout the severalviews.

Referring to. thel drawings the numeral 5 designates the base of a lirepot which may be mounted on supports 6 and is provided with a horizontalfuel inlet passageway 7 that is connected at one end with a tubular fuelinlet pipe 8 and terminates at its other end in an opening 10 disposedin the top of the base member and arranged centrally with respectv tothe fire pot.

The base 5 is provided with a flange 11 to which are rigidlysecured.three or more equidistantly spaced rigid upright posts 12 thatserve to support an annular track mem- I ber 13. The track member 13isin-turn providedat points mid-way between the posts 12 with three ormore other posts 14 that'projec't upwardly therefrom and are threadedfor the reception of nuts 15 and 16 which serve to support a medial repot section 18 and an upper re pot section 20. A lower fire pot section17 is supported for rotation on the track member 13 as hereinafterdescribed and a cap member 21 as arranged to rest upon washers 19 thatspace it slightly from the upper fire pot section 20 and issecured-against displacement by the ends ofthe posts 14 which projectupwardly thereinto.

The upper fire pot section 20 is provided around its upper edge with anexternally movement on bearing balls 27 that are disposed within asuitable ball race in the inner edge of the track member 13.

By the arrangement just described the sevf eral sections of the fire potare supported in slightly spaced relation to afford adjustable air inletpassageways therebetween the lower fire 'pot section 17 being separatedby. an air space 28 from the base member 5, the medial fire pot section18 being separated by an air inlet space'30 from the lower section 17,thevtop fire pot section 20 being separated by an air inlet space 31from the medial section and the cap member 21 being separated by an airinlet space 32 from the upper fire pot section 20. The air inletopenings 28, 30 and 31 eachextendl 'entirely around the fire pot and maybe adjusted .as to width by adjusting the nuts on the posts 12 and 14.

The cap member angular or beveled 21 is provided withan surface 33 whichgives a flaring effect to the top of the fire pot and with a larger airhighly heated and to ignite which merges into a horizontal shelf 34 overwhich the ashes'tmay -be discharged. The angular wall 33 is providedwith a plurality of small perforations 35 that communicate with anair/chamber 36 in the cap member. the air chamber 36 communicatingchamber 38 by. means of the passageway 32 which is of such narrow widthas to have the effect of reducing the air pressure inthe chamber 36.

The outer wall of the air chamber 38is formed by an annular drum 39 thatextends between and is tightly connected with the peripheral portion ofthe cap 21 and the peripheral portion of the flange 11.

The horizontal shelf 34 at the top of the cap member 21 is provided withan annular roove 40 wherein is disposed an electric igniter 40' whichmay be caused lby the passage of current therethrough to become the coalthat is in contact therewith thereby constituting a simple and efiicientmeans fire.

The interior of the lower fire pot section 17 is provided at a plurality,of points with lugs 41 that are recessed for' the reception of verticalposts 42 which project upwardly substantially to the plane of the upperedge of' the upper ire pot section 20 and cause the coal in the fire potto be rotated in unison with the lower lire pot section 17. In practicefour of the posts give very good results although it is obvious thateither a greater or less number may be used if desired. f

The upper fire pot section 20 is provided with a rigid internal spiralledge or screw thread 43 arranged so that when the rotating coal comesin contact therewith/the coals on the outer edge of the body of rotatingcoal will be depressed or worked downwardly toward the center of thefire pot by the thread and will serve to ignite the main bodyof coalbefore it reaches the top of the fire ot. i 'i Tige lower fire potsection 17 is provided withan annular gear rack 44 that meshes with anidler gear 46 which, in turn, meshes for lighting thel 42 have beenfound to pawl 52 on an arm 53 the lower end of which v is looselypivoted on the shaft 48 and the upper end of which is articulated withone end of a link 54 whose other end is connected with a crank pin 55 ona gear wheel 56 that is arranged to mesh with a small pinion 57 on ashaft 58j The shaft 58 is mounted -in brackets 60 :and carries airelatively large, fixedly mounted belt pulley 61 that is connected by vabelt'62 with a relatively small belt pulley 63 on the shaft 64 of amotor 65.

The engagement of the pawl 52 'with the teeth ofthe ratchet wheel 51 iscontrolled by a dog 66 that is arranged to rest on the teethof therachet wheel 51 and one end of which is pivoted to a plate 67 that isprovided with a handle 68 by which it may be lmoved about a centralpivot to adjust the position of the dog 66.' As the pawl 52 is movedback and forth by oscillation ofthe arm 53 it will ride over the dog 66and will only engage the teeth of the ratchet wheel 51 when it drops offof the end of the dog 66, hence if the dog is moved in a contraclockwisedirection as viewed in Fig. 3, it will lift the pawlfor agreater portionof its stroke and WilLretard the turning of the shaft 48 and vice versaif the dog 66 is moved in a clockwise direction far enough so that itwill not engage with and lift the pawl at all a maximum turning effectof the `shaft in, response to a given oscillation of thearm 53 will beproduced.

Any desired means may be used for holding the plate 67 so that it willnot move after it has been adjusted to a desired position, as forinstance, said plate may have an arcuate slot 81 through whichVprotrude's a bolt 82 that is rigid with the hopper 49 and has a nut 83that may be tightened against the plate. f

Air for purposes of combustion is supplied by a rotary fan within ahousing 70 which is connected by a/tubular conduit 71 lwith an airpassageway 72 that surrounds the coa-l feed tube 8 and communicates withthe air chamber 38 around the fire pot. The fan in the housing 7 may beconnected with the motor shaft 64 whereby it may be driven.

The passage of air through the conduit 71 may be controlled by abutterfly valve 73 that is mounted on a shaft 74 and is arcombinedaction of a weight 75 on a lever arm 76 andapin 77 on anotherflever arm78 the said pin beingarranged to engage a cam surface 80 on the plate67kwh\ereby when the plate is moved to reduce the'lspeed of rotation ofthe shaft 48 that governs the coal feed the valve 73 will be closed bythe action of the weight 7 5 and when the plate is moved to increase thespeed lof rotation of the shaft 48 the butterflyV valve 73 will beopened.

In' practice it has been found that the relative' proportion of coal andair are not constant as the rate at which these two elements are fed tothe furnace is increased or decreased but that as the feed of coal tothe furnace increases the proportional feed of air decreases and viceversa. Forpinsta-nce if the feed of coal to the furnace is; doubled itmay only be necessary to increase the feed of air by one half to securethe best results. The cam 80 is so shaped as to automatically cause thecorrect adjustment of the air when the feed of coal is-increased ordiminished.

ln operation the iire pot and passageways leadinv from the coal hopperthereto are normaIly filled with coal. IVhen it is desiredvto produce afire, current may be admitted to the electric igniter 40 to light thecoal at the topof the fire pot and the motor 65 may be started to feedcoal and air and to rotate the body of coal in the fire pot. The coalwill ignite around the top edges and the fire will very quickly spreadover the entire top of the fire pot which will become a glowingmass ofcoals. Y

As the mass of -coal is rotatedsome of the live coals from the top willbe caught beneath the screw thread 43 and moved downwardly therebytoward the center of the fire pot where they will serve to ignite theupwardly moving mass of coal so that by the time the coal reaches thextop of the fire pot it will be in condition for substantially perfectcombustion and will burn with intense heatand practically no soot-andsmoke;

The arrangement of the'air inlets in cascade formation and theautomatically balanced forced air and fuel feed system insures thatthere' will be a ysufficient supply of air at all points to properlyunite with the carbon in the coal and form the gases most conducive toperfect combustion.

The narrouT passageway 32 through which air passes from the large airchamber'SSto the smaller air chamber 36 in the cap member 2l serves toreduce the pressure in the chamber 36 and prevent too Strong a draftthrough the openings 35, thereby constituti ing means for supplying airat different pressures to air passageways located at differentelevations with respect to the fire pot. Y

The intermittent movement of rotation of the body of coal, the action ofthe posts 42l and the impingement of the coal on the screw thread 43,keep the coal broken up and prevent the formation of any clinkers thatmi ht otherwise have a tendency to form.

his apparatus is particularly well adapted to be constructed in smallunits for the use inl heating homes but it will be understood that thesame may be constructed inl larger sizes if desired.

It is obvious that changes in the form of construction and arrangementof the vari-` -ous parts of this device may be resorted to within thescope of the following clalms.

l. An underfeed furnace, comprising a circular fire pot, means forfeeding fuel upwardly into said fire pot and means for effecting thedepression within said fire pot of the peripheral portion of the fuel.

2. An underfeed furnace of the class described comprising a circularfire pot, means for feeding fuel upwardly within saidmfire pot, meansfor effecting the rotation ofisuch fuel and vmeans for causing thedownward movement of the said fuel.

3. A11 underfeed furnace comprising a fire pot, means for effecting therotation of a body of fuel within said fire pot, and a rigid spiral ribon the interior of said fire pot for engaging with and depressingportions of said rotating body of fuel.

4. In an underfeed furnace a sectional fire pot comprising rigid uppersections and a rotatable lower section, projecting devices on saidrotatable lower section for rotating the bodyl of coal in said fire potand a spiral thread on said upper fixed section for moving coals ontheperipheral portion of said rotating body of coal downwardly.

5f In an underfeed furnace a fire pot comprising rigidly mounted uppersections, a ro-l tatably mounted lower section having a central opening,means for feeding coal upwardly through said central opening, postsrigid with said rotatable lower section and -sageways therebetween, andmeans for ad-v justing said sections to vary the size of said air inletpassageways.

7. A furnace of the class described comperipheral portion of the prisinga stationary base member, a lower y fire pot section supportedl forrotation and spaced a slight distance above `said base member, a medialfire pot section rigldly supported at a slight distance above said baseSection5 an upper iire p'ot section rig idly Supported at a slightdistance above said medial sectionr and means for adjusting the spacesbetween," all of said sections.

8. An underfeed furnace comprising a re pot formed of a plurality ofsuperimposed sections independently and adjustabl7 supported inlslightly spaced apart relation one above another to leave relativelynarrow annular air inlet passageways therebetween, means for feedingcoal upwardly into said fire pot, a jacket surrounding said fire potsections and spaced therefrom to form an air chamber, and means forintroducing air underpressure into said air chamber.

9. In an underfeed furnace the combination with a fire pot, of means forforcing fuel upwardlyl through said lire pot and an electric ignitingelement disposed at the upper peripheral edge of said fire pot andarranged to ignite the fuel.

Signed at Seattle, NVasliington, this 20th day of May, 1919. f

MERLE J. WiGHTMaiN. p

